24t . "- CALORIC. 



and appear full, but will return to its former state 

 by withdrawing it from the fire. From this pro- 

 perty of matter in expanding by heat, the thermO" 

 meter becomes a measure of the heat in bodies. 



Every body, therefore, whether solid, liquid, or 

 gaseous, is augmented in all its dimensions, by an 

 increase of sensible heat : and on the contrary, all 

 bodies contract by an abstraction of caloric. We 

 are still very far from being able to produce the 

 degree of absolute cold, or total deprivation of 

 heat ; hence, we are incapable of causing the ulti- 

 mate particles of bodies to touch each other. 



It may be supposed, since the particles of bodies 

 are thus constantly impelled by heat to separate 

 from each other, that they would have no con- 

 nexion between themselves ; and that, of conse- 

 quence, there could be no solid body, unless the 

 particles were held together by some power which 

 tended to unite them ; this power is the attraction 

 of cohesion. Thus, the particles of all bodies 

 may be considered as subject to the action of two 

 opposite powers, repulsion and attraction^ between 

 which they remain in equilibrio. So long as the 

 attractive force remains strongest, the body must 

 continue in a state of solidity ; but if, on the con- 

 trary, heat has so far removed these particles from 

 each other, as to place them beyond the sphere of 

 attraction, they lose the cohesion they had before 

 with each other, and the body ceases to be solid. 



Water gives us a regular and constant example 

 of these facts. Whilst below 32° it remains solid, 

 and is called ice. Above that degree of temper- 

 ature, its particles being no longer held together by 

 reciprocal attraction, it becomes liquid ; and when 

 we raise its temperature above 212**, its particles 

 giving way to repulsion caused by the heat, assume 



\ 



